Why did Joseph want a quiet divorce?

In today’s Gospel (Mt 1: 18-25), Joseph is unwilling to expose Mary to shame and therefore decides to divorce her quietly.

Since Joseph was already Mary’s husband (v19), what is the source of the shame?

Common explanation is that she was pregnant and unwed (only betrothed v18), but v19 seems to indicate otherwise.

Why the need for the divorce? Joseph could have simply remained silent, remained with Mary and there would be no shame at all since they were married.

Blessings

Mary and Joseph were betrothed, they had not yet begin to live together. As the NAB’s commentary on Matthew 1:18 states:

betrothal was the first part of the marriage, constituting a man and woman as husband and wife. Subsequent infidelity was considered adultery. The betrothal was followed some months later by the husband’s taking his wife into his home, at which time normal married life began.

It would have been a few months before Mary and Joseph lived together and lived a normal marital life, therefore it would have been obvious to everyone that the child was not Joseph’s. Joseph obviously knew the child was not his so he would have been very hurt to discover that Mary was pregnant.
Joseph was a human being with emotions and feelings, finding your betrothed is pregnant and its not your child is quite an emotional hit. According to the law he could have had Mary stoned for adultery (Deut 22:21-23) but he loved Mary and didn’t wish harm to come to her.

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